Appeal 3280211

The appeal is dismissed.

Despite the description of development set out above, I consider the description found on the Decision Notice and the Appeal Form better reflects the scheme that is before me and that which the Council considered. The development proposed is therefore for ‘Erection of rear mansard roof extension and 2no. dormer windows, single storey ground floor side infill extension and installation of 3no. front roof lights’. I have therefore dealt with the appeal on this basis.

Appeal decisions must be based on the policies from the development plan prevailing at the time of determination. Policies Q5, Q8, Q11 and Q22 of the Lambeth Local Plan (September 2015) and the Draft Revised Lambeth Local Plan 2020 referred to on the Decision Notice are superseded by equivalents from the Lambeth Local Plan 2020-2035 (LP) (22 September 2021). The appellant was made aware of the changes and given opportunity to comment upon their relevance to the appeal.

The National Planning Policy Framework was revised on 20 July 2021 (the Framework). I have had regard to the Framework in my decision and I am satisfied that this has not prejudiced any party, particularly as the revisions do not alter the policies upon which this appeal turns.

Planning permission has previously been granted for the single storey ground floor side infill extension and front roof lights, as part of a proposal which also included two linked dormer windows1. The Council does not object to those elements of the appeal scheme that already have permission. The main issue is therefore the extent to which the proposed rear mansard roof extension and 1 Planning Reference: 21/00016/FUL. dormer windows would preserve or enhance the character or appearance of the host property, street scene and the Minet Estate Conservation Area.

The appeal concerns a two-storey mid-terraced house situated to the southern side of [address] and is within the Minet Estate Conservation Area (CA), which covers a residential area of late-19th Century origin situated around the perimeter of Myatt’s Field Park, a [name] listed Register Park and Garden. The CA incorporates a richness and variety of articulation, but a fine-grain that is coherent and repetition in its materials and motifs. The CA retains much of its historic quality, principally due to the freehold of the Estate being privately managed up until the late 1960s, when it was taken on by the Council.

The terrace (Nos 1-9, consecutive) is designed with elegant proportions and fine detailing, including variety in projecting and recessed features across the plane of the front façade and embellishment of the roofscape through gables, pinnacles, and finials. The second and third houses at either end also incorporate mock gabled parapets and there are prominent towers to either end of the terrace. The roof is dual pitched with tall chimneys and parapets are arranged between houses and at the end of the terrace. These features are predominantly experienced from the front in [address], which has a visual connection with Myatt’s Field Park to the west. Meanwhile, at the rear of the terrace, each house incorporates a projection of some length. These are mostly paired and of two storeys but set down from the main ridge and feature canted bays at the very rear.

Many of the roofs of the houses have been altered, in a piecemeal fashion, with rooms formed in the attic space, the quality of which varies. Some feature inappropriately scaled and detailed box dormers, whilst others incorporate sympathetically designed individual or linked dormer windows. There are also front and rear rooflights.

There is some variation to the roof form of properties within the CA and the Minet Conservation Area Character Appraisal2 (MCACA) refers to some of the key buildings that do not include traditional pitched roofs. In particular, [address], a fine locally listed building situated to the northern side of [address], was designed and built with a mansard roof across the whole of the building, behind a cornice and with dormer windows aligned with those beneath. Immediately to its west is a more modern block of flats also incorporating a mansard roof, but this extends to the eaves, which overhang the top of the brickwork beneath, as such it is poorly articulated. There are also other properties with mansards used as features, many of which are French inspired, such as at Nos [address].

The rear gardens of the properties form the boundary of the CA but the MCACA does not reference the rear of the houses in [address]. The part of this road which continues behind the terrace is also not a busy thoroughfare and views toward the rear of the appeal property and wider terrace are impacted upon by garden walls and vegetation. Nevertheless, views into the CA are still available from the road and residential properties to the south and west. 2 January 2018. Despite the collective value of the roofscape of the terrace being diminished by some poor alterations, the majority still enable the original form of the roofs of the houses to be appreciated from within the locality.

Given the above, I find that the significance of the CA, insofar as it relates to this appeal, to be primarily associated with the contribution made to the character and appearance of the CA by the architecture of the street façade of the terrace and the intact and sensitively altered elements of its roofscape, including that of the appeal property.

The appeal property is not a heritage asset but this is not a determinative factor as the Council’s SPD3 confirms that the advice in the document relating to heritage assets also includes properties within conservation areas. However, the rigid interpretation of the unacceptability of mansard roofs in conservation areas is unlikely to be malleable enough to deal with circumstances where the roof form of properties would enable them to be added. This point is evidenced by the fact that the Council have granted permission at various locations in other conservation areas across the Borough4. While details of the context of each of those permissions is not before me, it is clear that mansards are an original distinctive element of the architectural design of some buildings within the CA, and these make a significant contribution to its townscape qualities.

The proposal has been designed by award-winning local architects and I have no reason to doubt that the mansard would meet the tests outlined in the Council’s SPD and it would be constructed with a sensitively chosen palette of high quality, durable materials, that would closely reflect those used in the construction of the existing terrace. Nevertheless, as evidenced by the linked dormer windows installed at No 6, there are fundamental differences between the approved and appeal schemes. In particular, the historic rear roof form of the existing property would remain apparent around the linked dormer windows. In contrast, the form, scale, and mass of the projection associated with the proposal, beyond the plane of the roof slope, would jar with the coherent prevailing characteristics of the roof of the terrace.

The proposal would not be visible from the front of the house, but it would be visible at the rear. This would be in the context of the more poorly executed alterations further to the east. However, their existence would not provide justification for a further development that I consider would appear as a dominant and incongruous form of development which would cause unacceptable harm to the character and appearance of the appeal property and the contribution it makes to the wider roofscape of the terrace and the CA.

The statutory duty in Section 72(1) of the Planning (Listed Building and Conservation Areas) Act 1990 (the Act) is a matter of considerable importance and weight. Paragraph 197 of the Framework states that the desirability of sustaining and enhancing the significance of heritage assets and putting them to viable uses consistent with their conservation should be taken into account 3 Building Alterations & Extensions Supplementary Planning Document (September 2015). 4 [address] (ref: 20/00616/FUL), [address] (20/01124/FUL), [address] (20/01363/FUL), [address] (20/03038/FUL), [address] (21/02079/FUL) and [address] (21/02138/FUL). in determining applications. Paragraph 199 of the Framework also advises that when considering the impact of development on the significance of designated heritage assets, great weight should be given to their conservation.

The proposal would be harmful to the character and appearance of the CA, which would have a negative effect on its significance as a designated heritage asset. While the harm that would be caused to the CA would be localised, it would equate to less than substantial harm to the significance of the CA. In such circumstances, paragraph 202 of the Framework identifies that this harm should be weighed against the public benefits of proposals.

The proposal would enable improvement to the internal living environment of the appellants’ house, including an additional bedroom and bathroom, but with a lesser amount of disruption to the existing functionality of the house than the approved scheme. This would also enable greater possibilities for working from home. These alterations would therefore better meet the needs of the appellants and their family, while maintaining the internal integrity of the home, but they would be largely private benefits.

Like the approved scheme, the proposal would also ensure maximum insulation, which has the potential to improve the energy efficiency of the existing roof structure. Given the extent of the development, this would only equate to a limited public benefit in environmental terms.

Taking the above together, the public benefits I have outlined above would not justify allowing development that would fail to preserve or enhance the character and appearance of the CA. Therefore, in accordance with paragraphs 199 and 202 of the Framework, considered together, I conclude that the public benefits do not outweigh the great weight to be given to the less than substantial harm that I have identified.

In light of the above, I conclude that the proposed rear mansard roof extension and dormer windows would fail to preserve or enhance the character or appearance of the host property and the Minet Estate Conservation Area. Hence, the appeal proposal would fail to satisfy the requirements of the Act, paragraphs 197 and 199 of the Framework and conflicts with the design and heritage aims of Policies Q5, Q8, Q11 and Q22 of the LP.

The approved scheme, of March 2021, included the side infill extension and roof lights. [name] to allow those elements of the appeal scheme, the effect would be to create a new planning permission for those elements and the appellants would have choice over which permission to implement. However, given that those parts of the proposal are identical in the appeal scheme, there would be no beneficial outcome from allowing permission for them.

For the reasons given above, I conclude that the appeal should not succeed.